Sugar; mollify (7)
I believe the answer is:
sweeten
I believe this is a double definition.
'sugar' is the first definition.
(I know that sugar is a more specific form of the action sweeten)
'mollify' is the second definition.
(thesaurus)
(Other definitions for sweeten that I've seen before include "Make saccharine or honeyed" , "placate" , "Make more agreeable or acceptable" , "Modify" , "Add, eg, sugar to" .)